Calorie restriction not the only way to increase longevity

1 February 2006

New research carried out by University College London (UCL)
scientists has found that it is possible to increase life expectancy by
50% without decreasing calorie intake – at least in fruitflies. The
research adds new complexity to the established view that dietary
restriction works to extend life span by reducing calorie intake. This
report reveals that the nutritional source (ie fat, protein,
carbohydrate) of the calories is more important to longevity than a
reduction in the total calories consumed.

The study published on 30th May 2005 in PLoS Biology, shows that
fruitflies - ‘Drosophila’- can live longer without reducing calories
but instead by consuming proportionally less yeast (which is the flies’
only source of protein and fat). The team, led by Professor Linda
Partridge of UCL’s Centre for Research on Ageing, Department of
Biology, believes that this demonstrates that calorie intake is not the
key factor in the reduction of mortality rate by dietary restriction in
this species.

The authors restricted the diet of the fruitflies by diluting the
nutrients in the fly’s standard lab diet of yeast and sugar to a level
known to maximize life span. Since both yeast and sugar (carbohydrates)
provide the same calories per gram, the authors could adjust nutrient
composition of the yeast/sugar mixture without affecting the calorie
count, allowing them to separate the effects of calories and nutrients.

Reducing both nutrients increased the flies’ life spans, but yeast
had a much greater effect: reducing yeast in the mixture from 150 grams
to 65 grams increased median life span by over 60%, compared to just 9%
when calorie intake was reduced to the same extent by lowering sugar
levels. Late-starters on the restricted-yeast diet gained the same
benefits as the rest of the yeast-deprived group. Forty-eight hours
after being switched from normal diets to yeast-restricted diets, flies
were no more likely to die than flies fed the yeast-restricted diet
throughout their adult life.

Professor Linda Partridge said: “Altogether these results make a
strong case that calories per se are not the salient factor in
prolonging life—at least in fruitflies. The dramatic impact of reducing
yeast suggests that protein or fat plays a greater role in fly
longevity than sugar. This suggests that yeast and sugar trigger
different metabolic pathways with different effects on life span. The
caloric-restriction/longevity paradigm is not as simple as current
scientific thought believes and needs more rigorous review.”

2. The paper “Calories Do Not Explain Extension of Life Span by
Dietary Restriction in Drosophila” is available online on PLoS
Biology’s website.
http://biology.plosjournals.org/perlserv/?request=index-html&issn=1545-7885

3. Report authors: Dr William Mair, Dr Matthew D. W. Piper and
Professor Linda Partridge of the Centre for Research on Ageing,
University College London, Department of Biology, London.